This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-160786, filed Jun. 8, 1999; No. 11-160787, filed Jun. 8, 1999; No. 11-229828, filed Aug. 16, 1999; and No. 11-229829, filed Aug. 16, 1999, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of manufacturing a photovoltaic module in which an encapsulating material encapsulates a semiconductor cell provided on a glass substrate.
There is a non-single-crystal type photovoltaic module in addition to a crystal type photovoltaic module which uses single crystaline silicon or polycrystal silicon. In either type, silicon tends to encourage chemical reactions and is weak against physical impacts.
Hence, a structure in which the semiconductor cell formed in the photovoltaic module is laminated with an encapsulating material containing, as a main component, ethylene vinyl acetate copolymer (hereinafter abbreviated as EVA) or ethylene vinyl acetate triallyl isocyannulate ternary copolymer bridge material (hereinafter EVAT) has been adopted for the purpose of protecting silicon or the like.
Japanese Patent Application KOKAI Publication No. 10-95089 discloses a conventional apparatus in which a photovoltaic module is laminated with an encapsulating material such as EVA or EVAT.
In general, in this kind of apparatus, an upper chamber including a diaphragm and a lower chamber including a heater table are arranged so as to be opened and closed relative to one another. The heater table and the diaphragm pressurize and heat the photovoltaic module and the encapsulating material so as to integrate them together.
At this time, the substrate of the photovoltaic module is directly heated on one side surface thereof while the encapsulating material provided on the other side surface is heated indirectly by heat transfer from the heater table through the substrate. Therefore, a temperature difference appears between both surfaces of the substrate in the heating process, so the substrate is easily warped due to the temperature difference. Consequently, end portions of the substrate are damaged during pressurization or the entire substrate is not heated uniformly in some cases.
Therefore, conventionally, a lamination unit to be laminated, comprising a photovoltaic module and an encapsulating material, are pre-heated by a pre-heater and then conveyed into the chamber.
If the lamination unit is thus pre-heated, the temperature difference between the substrate and the encapsulating material can be smaller compared with the case of no pre-heating.
After pre-heating by the pre-heater, the lamination unit to be laminated is heated by the heater table and the diaphragm provided in the upper chamber is elastically deformed to make the diaphragm contact the lamination unit. Pressurizing and heating are thus performed.
However, the temperature of the diaphragm is normally very low compared with the heater table. If the diaphragm is deformed to contact the lamination unit to be laminated, this diaphragm absorbs the heat of the lamination unit.
Thus, the lamination unit to be laminated has a relatively large temperature difference between the surface on the side contacting the heater table and the other surface on the side contacting the diaphragm. As a result, the substrate becomes warped due to the temperature difference between the surfaces of the lamination unit. If the warped substrate is pressurized and heated, the substrate is damaged or the temperature of the lamination unit becomes uneven. In particular, the uneven temperature makes the thermal contraction of the encapsulating material uneven thereby causing wrinkles.
Meanwhile, the encapsulating material is formed like a sheet by extrusion molding and is wound up by a wind roller after the molding. This material is cut into a predetermined size when it is used.
Because the encapsulating material is thus subjected to extrusion molding and wound up on a wind roller, a residual stress unavoidably stays in the encapsulating material. Therefore, if the part to be laminated which comprises a photovoltaic module and an encapsulating material layered during the laminating process, the encapsulating material contracts due to the residual stress in some cases.
As a result, wirings of the semiconductor are misaligned or the encapsulating material is wrinkled so defective products are created due to deteriorated outer appearance.
The present invention hence has an object of providing a method of encapsulating a photovoltaic module, which is capable of uniformly heating and thereby laminating a lamination unit comprising the photovoltaic module and an encapsulating material.
Another object of the present invention is to provide a photovoltaic module and a method of encapsulating the same in which contraction is not caused when pressurizing and heating a lamination unit comprising a photovoltaic module and an encapsulating material to laminate the lamination unit.
To achieve the above objects, according to the present invention, there is provided a method of encapsulating a photovoltaic module utilizing a lower chamber containing a table having a heater, and an upper chamber having a diaphragm elastically deformable under a pressure, the upper chamber and the lower chamber arranged to open and close relative to one another. The method is designed to laminate a lamination unit having an encapsulating material and the photovoltaic module. The method comprises the steps of: pre-heating the diaphragm to a predetermined temperature; supplying the lamination unit onto the table; and pressing and heating the lamination unit by elastically deforming the diaphragm.
According to the method of encapsulating a photovoltaic module as described above, the lamination unit is heated such that one surface of the lamination unit which contacts a table and the other surface which contacts the diaphragm are heated to substantially equal temperatures. Accordingly, a temperature difference is difficult to occur.
The other objects and advantages of the present invention will be understood from the following description or embodiments of the present invention. Various objects of the present invention will be achieved by the structures clearly defined in the appended claims and combinations thereof.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.